This disclosure relates to an aliphatic-aromatic copolyester of poly(butylene-co-adipate terephthalate) from polyethylene terephthalate, compositions and articles containing the copolyester, and a process for preparing the copolyester.
Thermoplastic molding compositions based on polybutylene terephthalate (PBT) are used in various applications. Although useful to many customers, conventional PBT molding compositions generally cannot be made from recycled sources of PBT due to the lack of availability of large post-consumer or post-industrial supplies of PBT scrap materials. Polyethylene terephthalate (PET), unlike PBT, is made in much larger quantities and is more easily recovered from consumer wastes.
With increasing demand for conserving non-renewable resources and more effectively recycling underutilized scrap PET, improved and less costly processes for deriving PBT from scrap PET materials are sought, in particular if the resulting derived PBT compositions possess desirable physical properties such as tensile and impact strength, and thermal properties. It would be particularly advantageous if the process were compatible with PET blend compositions comprising other polymer components and/or impurities.
The present inventors have observed that biodegradable aliphatic-aromatic copolyester product obtained in the reaction was discolored, often ranging from pink to red in color. This presents a problem in that the aesthetic appearance of a non-white polymer product is an obstacle to employing the polymer in end-uses where the discoloration is apparent and cannot be readily overcome or masked with pigments, whitening agents or fillers.